1. Technical Field
The present invention relates to parts for internal combustion engines such as pistons and cylinder heads and methods of manufacturing the same.
2. Background Art
It is a general practice to use solid ceramics such as silicon nitride, zirconia, mullite, and aluminum titanate for a thermal insulator of parts for internal engines such as pistons and cylinder heads. One problem here is that, even though these ceramics are of sufficiently high strength, they tend to degrade volumetric efficiency of the engine because of their high thermal conductivities.
Ceramic materials having a small thermal conductivity, on the other hand, are available in the form of foamed ceramics and laminates made from ceramic fibers. However, since their strength is no more than several tens of kgf/cm.sup.2, they cannot withstand the firing pressures that are generated by the combustion of fuel.
Subsequently, heat insulating composites made from inorganic fibers and/or hollow particles with a coating material prepared from a metallic alkoxide as the binder have been devised to correct these drawbacks, but a deficiency with these materials is that they need to be dried for a long period of time prior to the baking process.